Stabilization



Patented hiya- 1950 oral-cs STABILIZATION Louis I. Hansen Minneapolis, and cum Smith, in, Akron, Ohio, assi nors to m Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Application August 6, 1947, Serial No. 766,880

19 Claims. (CL 260-45-75) This invention relates to the stabilization of rubber-like copolymers of a conjugated diene and a vinyl compound (or methyl-substituted vinyl compound, viz., alpha methylstyrene and methacrylonitrile). The vinyl compounds include, for example, styrene, alpha methylstyrene, nuclearly substituted styrenes, monochlorostyrene, dichlorostyrene, vinylnaphthalene, vinylbiphenyl, vinyl carbazole, 2-vinyl-5-ethylpyridine, 2 ethyl 5 vinylpyridine, acrylonitrile, methacrylonitrile, etc. The conjugated dienes include, for example, 1,3-butadiene, isoprene, 2- cyanobutadiene-l,3, cyclopentadiene, piperylene, dlmethylbutadiene-1,3, 2-methylpentadiene, etc. More particularly, the invention relates to the stabilization of such copolymers with stannous salts of catechol and alkylated catechols. Such stabilizers afiect not only the uncured copolymers but also the vulcanizates; They have a beneficial effect on the coagulum obtained from emulsion copolymerization, during drying, storage, etc.

Various stabilizers have been used commercial-- ly with these rubber-like copolymers, and others have been suggested. Some discolor badly. The tests reported below show that not only are the stannous salts of catechol and alkylated catechols good stabilizers, but generally speaking, they are non-discoloring.

In the tests recorded below only certain catecholates are mentioned. The invention is not limited to the use of these but include stannous catecholates with hydrocarbon substituents having a total of zero to ten carbon atoms, including, for example, stannous-catecholate, stannous pmethylcatecholate, stannous p-ethylcatecholate, stannous p-isopropylcatecholate, stannous p-npropylcatecholate, stannous o-tert-butylcatecholate, stannous o-ethylcatecholate, stannous 4,6-dimethylcatecholate, stannous 4,5 -dimethylcatecholate, stannous trimethylcatecholate, stannous tetramethylcatecholate, stannous di-tertbutylcatecholate, the stannous amylcatecholates, the stannous hexylcatecholates', the stannous heptylcatecholates, the stannous octylcatecholates, the stannous nonylcatecholates, the stannous decylcatecholates, the stannous di-amylcatecholates, etc.

The compound referred to'herein at catechol is o-dihydroxybenzene, It is sometimes called pyrocatechin. The stannous compcunds'are referred to herein as salts because it is believed that One reason for believing that they are salts and not chelates is that they may be formed by dif- 2 ferent methods. The following examples are illustrative.

EXAMPLE 1 EXAMPLE 2 Ten grams of 'catechol (0.091 mole) were dissolved in an aqueoussolution of 7.3 grams of sodium hydroxide (0.182 mole). Seventeen and three-tenths grams of stannous chloride (0.091 mole) were dissolved in water and added to the first solution. The resulting slurry was acidified with acetic acid and the product filtered ofi and dried. Yield 20.3 grams.

Analysis.-Calc. for C6H402SD: Sn, 52.34 'per cent. Found, 51.75 per cent (microgravimetric).

Although the stabilizer may be added at any stage of the process of preparing or compounding or otherwise treating the copolymer, it is advantageously added to the latex and is thus incorporated in the coagulum obtained from the latex resulting from emulsion copolymerization of the monomers and consequently is efiective as an antioxidant during drying as well as thereafter. In each of the recorded experiments the stabilizer was added to the latex in 'a sodium oleate emul-- sion. The results of the experiments show that stannous catecholate and stannous alkyl-substituted catecholates are superior to stabilizers used commercially and identified herein as Stabilizer Nos. 1,2 and 3.

STABILIZATION OF GR-S Untreated rubber-like copolymer of 1,3-butadiene and styrene (known commercially as GR-S) is lacking in anti-oxidants such as occur in natural rubber and ages under conditions which have little efiect onnatural rubber. It is, therefore, desirable to add stabilizer to the latex in order to stabilize the copolymer during drying, storage, etc.

The following table records the results of tests conductedon different portions of the same latex, treated with difierent amounts of two of the stabilizers of this invention and of the commercial stabilizer identified herein as Stabilizer 1. No blankyoid oi stabilizer was used in the tests because it is well known that the copolymer loses all or substantially all of its rubber-like properties underthe conditions of the test. Them- 4 and conducting the test for 4 minutes at 212 F. As controls, Stabilizer No. 1 and another widely used commercial stabilizer, herein identified as Stabilizer No. 2, are employed. The figure in the following table in each case represents the Mooney plasticity.

TABLE II Drying and aging of copolymer Alter A 4 Da t ima- Drying 20 Hrs. a 75 0. 'i fl 0. an 'lben 351;; Antioxidant LIL-m2 Color Band Test MIA/212 Hand Test MIA/212 Hand mi Htannous ammo n wma No change. 31 No chan e. a No change. Stamina-No.2 44 Me ium 30 .d0... 84 Set up.

darkgraybrown. flfifltabillsorNoJ 47 Br wn-- 6 ....-d0 70 Sontnwhat I. up.

ples were dried for hours at 75 C. The results of drying are illustrative oi. what happens on drying at any elevated temperature. The dried coagula were then aged in a circulating-air oven at 90 C. for two days and tour days. Other samples were aged for one day at 120 C. The following table records changes in color which took place and changes in the physical properties or the copolymer as determined by a hand test which involved feeling and stretching the stock to see to what extent, if any, it had deteriorated.

The results (and particularly those in the last column obtained under very'drastic test conditions) show the Mooney value of the copolymer containing 2 percent stannous catecholate to be actually less than the original Mooney plasticity, which was 51. Both commercial stabilizers permitted considerable stiffening as shown both by the Mooney plasticities and the results of hand ests.

Tests were conducted on the vulcanizate using dlflerently compounded materials for comparison.

TABLE I Drying and aging of copolymer Stabilizer Btannom Cateeholste p-tert-Butyl-Cstecholate Stabilizer No. l

n drying 20 Hrs at Color White to"... Light cream.-. Cream- Brown. Brown. Bagg ge gt Nochlnge-- Nodnnce. Nochangm..- Nochsnge- N0changs.-.- Nochange. Aged:

Twodays- Color Lighteream-.- Light Cream Vgarylight Brown Brown.

cream. rown. r HandTest Nochsngm.-- Nochange. Nochange Nochange. Nochsnga.-. Nocbsngs.

our sys- Color Cream Verylight. Very light Verylight. Brown Brown. Hand'l N change um N m' n zfi N ch N h es o o o ge o snge. o ange.. oc e. dggnone dsyst IIPCL: Slightly set o--.. Bomewhatset Slightly Somewhat set Bomefitset d Test. up. up. set up. up. up.

The last test is very drastic. It developed color in even the best stabilizers, but the test stabilizers were better than the commercial stabilizer.

The tests recorded in the first table show exeellent copolymer color on drying and resistance to discoloration on aging when stannous catecholate is used as the stabilizer or antioxidant. The stannous alkyl-substituted catecholate, likewise, gives results superior to the commercial stabilizer although the results with the stannous catecholate are better. The fact that superior plasticity retention is imparted to the copolymer is particularly worthy oi note because nondiscoioring antioxidants are usually interior in this respect in synthetic rubbers to the better discoloring antioxidants, such as Stabilizer No. 1.

To further study the effect of stannous catecholate on plasticity. certain tests were conducted in a Mooney plastometer using the large rotor The first formula used, in which all parts are by weight. follows:

The stocks were cured'40 minutes, 60 minutes, minutes, and minutes, respectively, at 280 F. and then aged four days in an oven at 212 F. The tests recorded in the following table are an average of the results obtained with the diflerent cures.

TABLE III 49mg of oulcanizate 500 cent Per cent Elorizetionst a' Tomileltreulth 3m Stabilizer Normal am Normal Med mg}, um Aged g gi s catecholate was 100 2,000 no was as m an first see 211% 2,000 lue see us 836 are (The modulus and tensile figures in all of the tables herein reprelent pounds per square inch.)

Other stocks compounded according to the above formula and cured 80 minutes at 280 1''. were tested for hot elongation at 100 C. and 200 0. both before and after aging five days at 212 C. The results of the tests are given in the following table:

TABLE IV Per cent hot elongation Unaged Stock Aged Stock Stabilizer stannous catecholate--- 695 425 260 180 Stabilizer No. l 666 360 216 170 Tables I11 and IV show that the stannous catecholate is superior to the commercial stabilizer in that it gives better percentage retention of compared with stock identically compounded in which Stabilizer No. 2 was substituted for the stannous catecholate. The compounding formula follows:

The stocks were cured 30, and 70 minutes, respectively, at 290 F. and then'aged for four days in an oven at 212 F. The physical properties of the stocks subjected to difierent cures were av-- erased and are recorded in the following table.

TABLE V Physical properties of vulcanizate 200 Per cent Tensile Strength Per cent Elongation at Modulus Break Stabilizer Normal Aged Normal Aged {L a Normal Aged i g g stannous catecholate 416 710 1,136 1,440 127.0 496 405 81.9 Stabilizer No.2 386 606 1,110 1,050 94.6 e 610 376 73.6

tensile strength and elongation on aging, and it gives a stock having a higher normal and higher aged hot elongation. In addition to imparting these superior properties to the vulcanized rubber, the stannous catecholate does not discolor the copolymer during vulcanization or during aging of the vulcanizate. (See Tables VI and VII.)

For the next test the stannous catecholate was compounded with ingredients to produce a white stock, and the properties of the vulcanizate were The results recorded in the above table show that the stannous catecholate imparted to the vulcanizate better retention of tensile and elongation on aging than a widely used nondiscoloring commercial stabilizer. The tests reported in the following tables show that of the above stocks compounded with stannous catecholate and this Stabilizer No. 2, the test stock was superior from the standpoint of resistance to discoloration. The tests were conducted on stocks cured 50 minutes at 290 F.

TABLE VII Exposure to natural weathering to the latex resulting from copolymerization or 1.3-butadi'ene and styrene, with the results recorded below. The latex was coaguiated and ammmm dried for 20 hours at 75 C. The dried coagula sum 2 Months in Fiorlda+2 5 were then aged at 110 C. in a recirculating oven.

2%,? Change in color was noted and the amount of deterioration was determined by feeling and pulling. am m white m Stabilizer N0. 2 W88 used 88 8 control. A blank Stabilizer No. 2 Slightly creamy.-. m. containing no stabilizer was included for com- 10 parison.

TABLE VIII Copolymer drying and aging After Aging at 110 C. Stabilizer Alta- Drying 1 Day 2 Day: 4 Days Stannous 4,5-dimethyl-catecholate:

Color White Darkeream Med. light brown Gray brown. Hand Test No change No change No change No change. Stannous heptyi-catechoiate:

Color Very light pink. Cream color Dark cream Med. gray brown.

No change. No change.... No change No change.

Dark gray Gray brown... Gray brown Gray brown. No change. No change No change- Somewhat set up.

Very light gray Light brown Hand Test No Portion somewhat Somewhat hard- Somewhat hard-- hardened but en ened. rest imchanged.

The natural weathering test was conducted on tapered dumbbell strips stretched 12 /2 percent. The Florida exposure started in February in both instances, and the Ohio exposure in May.

Tests on the drying and aging or oopolymer containing other stabilizers is recorded in the following table:

TABLE IX Drying and aging copolumer Aging at 110 C. Alter drying 20 hrs. at 75 C. Stabilizer 2' days 4 days Color Color Band test Color Hand test Stannous amyl methylcatecholate Cream Light browrn- No change. Light hrown No change. Stannous diamylcatecholateu Light yellow do do .do Do. None Light brown--. Somewhat hardened.

1 Resinous in spots and the rest set up.

Stocks containing other stabilizers were similarly tested with the following results:

Several other stannous alkylcatecholates were tested as stabilizers by adding 2 percent of each TABLE X Drying and aging of copolymer After drying 2'0 hrs. at 76 C. Hand test after aging Stabilizer Color Band Test 2 days 4 days Btannous di(tert-butyl)-catecholate Light yellow No change Surftace shiny,

se up. Btannous, methyl, tert-butyi-catecholate Light green gray.. .-do No change Somewhat set i up. Stalmous heptyl-catecholate Very light pink.... do --do No change. None Very light gray -..--do Somewhat hardened S gmde welia t 10' 'Copolymer coaguia containing 2 percent of The reports oi several natural and artiiicia several of the above stabilizers were compounded u weathering tests on stocks heavily loaded with f ggg g g gig gg ggig gg g gsk zinc oxide are given. Each stock contained 2 properties of such stocks before and after oven 5 Percent 01 stabilizer addedtothe latex- The aging 4 days at 212 F. trols include a commercial stabilizer herein iden- TABLE x:

Phi/steal properties of vulcanizate Stamens 4- Stannous 4, Stamens 4, Btannous Stabilizer meth l ii-dlmeth ti-dimethylhop 1 g g catecho ate cetecholate cateeholste catecho te 800 cent Modulus:

ne 250 200 275 225 825 325 Ag 675 625 750 650 875 750 Tensile strength:

Unaged .4 l, 475 1,075 1, 400 l, 200 1,250 1, 250 Aged l, 475 II 400 l, 450 l, 300 l, 475 l, 550 Percent elongation at break: v

U g 610 580 580 540 480 no 425 420 420 400 ass 410 TABLE XII Physical properties of vulcanizate Tensile Per Cent Elongation 300% strength at break Stabilizer P C t Un- Per Cent Un- Uner agad Aged Increase aged Aged Aged Rag Stamens di(tert-butyl)catecholate 90 225 135 821') 1,015 o'oo use we Stannons methyl, tertbutyl-catecholate 90 315 225 1,060 1, 150 715 475 55.5 Stabilizer No. 2 205 530 325 825 975 475 375 78.9

TABLE XIII Physical properties of vulcanizate Tensile Per Cent Elongation 300% Mam! stren th at break Stabilizer P c t Un- Un- Unan aged Aged aged Aged and Aged Rage:

Stannous heptyimime 230 660 1, 260 1,290 535 400 75. 0 Stabilizer No. 2 325 865 1, m 1, 415 480 s90 81. 4

The physical properties of the stocks stabilized tified as Stabilizer No. 3. The tests of Tables with the stannous alkylcatecholates as recorded in the above tables compare favorably with the m and xv record t results of weathering stocks containing the commercial stabilizers. in Akron, Ohio.

TABLE XIV Natural weathering 2 Months Stabilizer 8 days, color Color Checkin! Front Back Stannous di(tert-butyl) -oatecholate N 0 change. No cbange No change-- Stannous methyl, tert-butyl-catecholatedo --do do Blight. Stabilizer No. 2 Dark cream. Light tan... Light tan Do; Stabilizer No. 3 No change" No change No change- D0.

TABLE xv Natural weathering l Month I 8 Dan Stabilizer Color eck- Front Back Btmnou i-methyi-catecholato. No change. No change. No change- None. Saigon! 4,5-dimethyl-mtechodo- ---..do do D stlaanriouaip-dimethyl-eatecho- ..--.'do do ..do Do. Bunn ous he l-cetocholate o d Do. Btnbiiilcl N Dirk m- Light tan--. Light tam- D0. Stabilizer No. 3.----. o Do.

TABLE XVI 20 TABLE XIX Artificial weathering Stabili 1 g Hrs. in Fade m Hrs. in Sun I Exposure stabilizer ometet at 125 F. lamp at 7 inches Stmnous di(tsrt-butyl)-catechointo No change. gtonnous giethyl, tert-butyicatocholate 113g. stamens heptylmtecholam"' gg ig dis 3 5 333 stabilizer ntfz'nn Light tan. 2 Tim Artificial weathering tests were conducted by exposure for diflerent lengths of timein a fadeometer and by exposure to a sunlap at 7 inches distance. Each stock contained 2 percent of stabilizer (based on the copolymer). The condition of the stocks immediately atter exposure is reported in columns A and the condition of the same stocks 2 months after exposure is re- Thus, the stabilizers of this invention are efiective in rubber-like copolymers of a. conjugated diene and a vinyl aromatic compound, before and s after aging, and in general may be said to be ported in columns B." nondiscoloring.

TABLE XVH Artificial weatherin l'adoomoter atl251". Bunlamp at7inches Stabilizer 6 Hours 10 Home 8 Route 16 Hours A n A. B A B A B Stmnousl-methyl Bleached Slightly dia- Slightly dis- Lighter-cam. Very s1. dis- Lightcream SLdisoolm-ed Light cream.

cateeholate. 1 "colored. colored. Btannous 4.5dido do do ..do Do.

methyl-catcdmolate. Btnnnous 4,6-di- Very slightly Light cresmdo Cream ..d0 .do do Cream.

methyl-miechoiate. discolored. v Stannous heptyl- Bleached ..do Ve sl. disdo do ..do do Do.

umholate' 2 Li m: 'r r23 Light brown Tan Light tan Tan Tim 322331285 13: 3:: miachiiiiii nth-east: matte-11:33:; Lizhtcream. sidiir'd Lightcrea m: Lissa-5:: Liglittsn.

The results of other weathering tests are re- STABILIZATION OF COPOLYMERS OF corded in the following tables: BUTADIENE AND ACRYLONITRILE The stabilizers of this invention may be used TABLE m 05 in rubber-like copolymers of 1,3-butadiene and Artifi ial th i acryionitrile or a homologue such as methacryionitrile, for example. The following tests were made with different stabilizers in copolymers Stabillur 533315 599; Egg-3, 15,; of different composition. Two percent of the different stabilizers (based on the weight of the Stmnous di(tert-butyl)-eate- Cream Light tan. p lymer) w re added to latex resulting from c oate. b 1 mm 1 d Do emulsion copolymerization of the monomers. :fifi W The stabilizers were added as sodium oleate 3mm!" No.2 t brown emulsions. Certain of the tests recorded below 13 ncstabilizev. but to which sodium oieate was added.

Each latex was coaguiated and the coagulum dried hours at 76 C. The coagula were aged in an oven for our daysat 90 C. The following tables record the results of tests on diflerent copolymers, that of Table XX containing 36% acrylonitrile and that of Table XXI containin percent.

in runs xxn an alkyiatecl catechol Sana used in copolymer of 36% acrylonitrile content:

TABLE XXII Copolymer drying and aging Alter Aging Color After Stabilizer Drying Color Hand Test Btsnnous tert-butyl- Brown Excellent. catecholate.

Stabilizer No. 1 Light brown.- Dark brown.. Do. None Light tan"--. Dirty brown" Poor.

In the following table a copolymer containing 30 percent acrylonitrile was used.

TABLE xxrn Copolymer drying and aging Alter Aging Stabilizer gag?- Color Hand Test Stsnnous tert-butyl- Light tan. Gray tan Good.

cateoholste. Stabilizer No. l Light brown.. Brown Do.

The stabilizers of this invention, therefore, compare favorably with the commercial stabilizer in their effect on the copolymers. They are relatively nondiscoloring.

Stocks were compounded with diil'erent stabilizers according to the following formula:

FORMULA3 Copolymer containing 2% stabilizer 100.00 Coumarone resin 7.50 Sulfur 1.00 Magnesium oxide 5.00 Zinc oxide 85.00 Neutral clay 20.00 Titanium dioxide 20.00 1.30

Accelerator The copolymer used contained36 percent acr'y onitrile. The stocks were cured 40 minutes at 280 F. They were subjected to aging in natural and artificial light. For aging in natural light tapered strips were elongated 15 percent and exposed to Florida sunlight and weather for two months. Stock containing stannous catecholate remained white, whereas that containing Stabilizer No. 1 became gray brown.

The artificial weathering tests were conducted by exposing strips of white vulcanizate for ten hours, in a fadeometer at 11, and by exposing other strips to a. sunlamp for sixteen hours at a distance or 7 inches. The results are recorded in Tables XXIV and XXV.

TABLE XXIV Artificial weathering Fadeometer at Sun lam at 7 Stabilizer 0 F. as

Cream Brown Light cream...

Btannous cateoholate Btabiliser No. 1 None Light cream. Gray brown. Light cream.

TABLE xxv Artificial weathering Fadeometer at Sun lam at 7 stabilize 125 F. inch s Btannous itert-butylcatecholate.

L t cream. Stabilizer No. 1 uh Grey brown.

Light cream... Light cream.

The stabilizers, of this invention are shown by the above tests to. be relatively nondiscoloring. Copolymer containing 30 percent acrylonitrile was treated with 2 percent of stabilizers before coagulation and the coaguia compounded as 7 follows FORMULA 4 Copolymer containing 2% stabilizer 100.00 Sulfur 2.00 Carbon black 50.00 Stearic acid 3.50 Zinc oxide 5.00 Accelerator 1.30

The stocks were cured 60 minutes at 274 F. and then aged in an oven for four days at 212 F. and also aged in an air bomb (60 lb. air) for ten hours at 260 F. The stocks were then tested and their properties recorded in the following table:

TABLE XXVI Physical properties 0] vulcanizate Stannous Stabilizer catecholate Btabiliner N o. 1

Before Aging:

Modulus at 300%.-.. Tensile strength Per cent Elongation Alter Oven-Aging:

Tensile strength Per cent Elongation at break Alter Air-Bomb Aging:

Tensile strength Per cent Elongation at break ten.

Usually, about 1.0 to percent of the stabilizer,

will be used with any of the copolymers included herein. The stabilizer may be used in smaller amount with another stabilizer. Generally speaking, from 0.1 to 10.0 percent of the stabilizer may be used, based on the weight of the copolymer. The examples are illustrative. The invention is defined in the appended claims.

The stannous alkyl catecholates are claimed as new compounds in Smith application Serial No. 43,529, filed August 10, 1948. The preparation of stannous catecholates by making alkaline a solution of a catechol and a stannous salt of a mineral acid is claimed in Smith Serial No. 28,728, filed May 22, 1948.

' What we claim is:

l. A rubber-like composition which is essentially copolymer of 1) a conjugated diene from the class consisting of 1,3-butadiene,-isoprene, 2- cyancbutadiene-1,3, cyclopentadiene, piperylene, dimethylbutadiene-1,3 and 2-methylpentadiene, and (2) a compound of the class consisting of styrene, alpha methylstyrene, nuclearly substituted styrenes, vinylnaphthalene, vinylbiphenyl, vinyl carbazole, 2-vinyl-5-ethylpyridine, 2-ethyl-5-vinylpyridine, acrylonitrile and methacrylonitrile, which copolymer is stabilized by a small amount of a stannous salt of the class consisting of the catecholate and those alkylcatecholates in which the total of the carbons in the alkyl groups is one to ten. r

2. Cured rubber-like copolymer of 1,3-butadiene and styrene stabilized with a small amount of stannous catecholate.

3. Cured rubber-like copolymer of 1,3-butadiene and styrene stabilized with a small amount of a stannous alkylcatecholate in which the total of the carbons in the alkyl groups is one to ten.

4. Cured rubber-like copolymer of 1,3-butadiene and acrylonitrile stabilized with a small amount of stannous catecholate.

5. Cured rubber-like copolymer of 1,3-butadiene and acrylonitrile stabilized with a small amount of a stannous alkylcatecholate in which the total of the carbons in the alkyl groups is one to ten.

6. Uncured rubber-like copolymer of 1,3-butadiene and styrene stabilized with a small amount of a stannous salt of the class consisting of the catecholate and those alkylcatecholates in which the total of the carbons in the alkyl groups is one to ten.

7. Uncured rubber-like copolymer of 1,3-butadiene and acrylonitrile stabilized with a small amount of a stannous salt of the class consisting of the catecholate and those alkylcatecholates in which the total of the carbons in the alkyl groups is one to ten.

8. Nondiscoloring rubber-like composition composed essentially of copolymer of a conjugated diene monomer and a vinyl aromatic compound stabilized with a small amount of a stannous salt of the class consisting of the catecholate and those alkylcatecholates in which the total of the carbons in the alkyl groups is one to 9. Nondiscoloring rubber-like composition composed essentially of copolymer of a conjugated diene monomer and a monomer of the class consisting Of acrylonitrile and homologues thereof, which copolymer is stabilized with a small amount of a stannous salt of the class consisting of the catecholate and those alkylcatecholates in which the total of the carbons in the alkyl groups is one to ten.

10. The process of stabilizing a rubber-like copolymer of a conjugated diene and a vinyl monomer. which comprises mixing therewith a small amount of a stannous salt of the class consisting of the catecholate and those alkylcatecholates in which the carbons in the alkyl groups total one to ten.

11. The process of producing rubber-like coagulum which comprises mixing a small amount of stannous catecholate with latex of a rubber-like copolymer of a conjugated diene monomer and styrene, coagulating and drying at an elevated temperature.

12. The process of producing rubber-like coagulum which comprises mixing with latex of a rubber-like copolymer of a conjugated diene monomer and styrene, a small amount of a stannous alkylcatecholate in which the total of the carbons in the alkyl groups is one to ten, coagulating and drying at an elevated temperature.

13. The process of producing rubber-like coagulum which comprises mixing a small amount of stannous catecholate with latex of a rubber-like copolymer of a conjugated diene monomer and acrylonitrile, coagulating and drying at an elevated temperature.

14. The process of producing rubber-like coagulum which comprises mixing with latex of a rubber-like copolymer of a conjugated diene monomer and acrylonitrile, a small amount oi a stannous alkylcatecholate in which the total of the carbons in the alkyl groups is one to ten, :oagulating and drying at an elevated temperaure.

15. The process of curing rubber-like copolymer of 1,3-butadiene and styrene which comprises heating the same with sulfur and as a stabilizer a small amount of stannous catecholate.

16. The process of curing rubber-like copoly- 1 comprises heating the same with sulfur and as stabilizer a small amount of stannous catecholate.

18. The process of curing rubber-like copolymer of 1,3-butadiene and acrylonitrile which comprises heating the same with sulfur and as stabilizer a small amount of a stannous alkylcatecholate in which the total of the carbons in the alkyl groups is one to ten.

19. The process of curing rubber-like copolymer of (1) a conjugated diene from the class consisting of 1,3-butadiene, isoprene, Z-cyanobutadiene-1,3, cyclopentadiene, piperylene, dimeth- 18 kylcatecholates in which the total of the carbons UNITED STATES PATENTS in the alkyl gmups is one t Number Name 1 Dhte LOUIS HANSEN- 2,310,443 Lightbown Feb. 9, 1943 GEORGE R SMITH 5 2,335,089 Sibley Nov. 23, 1943 REFERENCES CITED FOREIGN PATENTS The following references are of-rgcord in the Number Country Date me 9! this pdtent; 526,072 Great Britain Sept. 10, 1940 

1. A RUBBER-LIKE COMPOSITION, WHICH IS ESSENTIALLY COPOLYMER OF (1) A CONJUGATED DIENE FROM THE CLASS CONSISTING OF 1,3-BUTADIENE, ISOPRENE, 2CYANOBUTADIENE-1,3, CYCLOPENTADIENE, PIPERYLENE, DIMETHYLBUTADIENE-1,3 AND 2-METHYLPENTADIENE, AND (2) A COMPOUND OF THE CLASS CONSISTING OF STYRENE, ALPHA METHYLSTYRENE, NUCLEARLY SUBSTITUTED STYRENES, VINYLNAPHTHALENE, VINYLBIPHENYL, VINYL CARBAZOLE, 2-VINYL-5-ETHYLPYRIDINE, 2-ETHYL-5-VINYLPYRIDINE, ACRYLONITRILE AND METHACRYLONITRILE, WHICH COPOLYMER IS STABILIZED BY A SMALL AMOUNT OF A STANNOUS SALT OF THE CLASS CONSISTING OF THE CATECHOLATE AND THOSE ALKYLCATECHOLATES IN WHICH THE TOTAL OF THE CARBONS IN THE ALKYL GROUPS IS ONE TO TEN. 